He is right, there is no cancel button to cancel your subscription. You'd have to report theft or fraud to your bank since I doubt you'd be able to get a human being on the phone at Adobe support to cancel your account for you.

There should be a link, but there is not. Unlike Creative Cloud, there is no button to cancel your PhoneGap Build subscription. Attempting to call Adobe led to just as much of a dead end. Until someone can demonstrate otherwise, it is currently an impossibility to cancel your subscription.